[Android] Use Alarm for timers in the main threadupstream/tmpsantos-alarm

Needed because of the restrictions of using util::Timer in the main
thread on Android, i.e. we don't have control over the ALooper timeout.

2 files changed, 4 insertions, 28 deletions

diff --git a/platform/android/src/run_loop.cpp b/platform/android/src/run_loop.cpp
index 3c605b70e8..77f9896e05 100644
--- a/platform/android/src/run_loop.cpp
+++ b/platform/android/src/run_loop.cpp
@@ -1,9 +1,8 @@
 #include "run_loop_impl.hpp"
 
+#include <mbgl/util/alarm.hpp>
 #include <mbgl/util/platform.hpp>
 #include <mbgl/util/thread_local.hpp>
-#include <mbgl/util/thread.hpp>
-#include <mbgl/util/timer.hpp>
 
 #include <android/looper.h>
 
@@ -56,28 +55,6 @@ int looperCallbackDefault(int fd, int, void* data) {
 namespace mbgl {
 namespace util {
 
-// This is needed only for the RunLoop living on the main thread because of
-// how we implement timers. We sleep on `ALooper_pollAll` until the next
-// timeout, but on the main thread `ALooper_pollAll` is called by the activity
-// automatically, thus we cannot set the timeout. Instead we wake the loop
-// with an external file descriptor event coming from this thread.
-//
-// Usually an actor should not carry pointers to other threads, but in
-// this case the RunLoop itself owns the Alarm and calling wake() is the most
-// efficient way of waking up the RunLoop and it is also thread-safe.
-class Alarm {
-public:
-    Alarm(ActorRef<Alarm>, RunLoop::Impl* loop_) : loop(loop_) {}
-
-    void set(const Milliseconds& timeout) {
-        alarm.start(timeout, mbgl::Duration::zero(), [this]() { loop->wake(); });
-    }
-
-private:
-    Timer alarm;
-    RunLoop::Impl* loop;
-};
-
 RunLoop::Impl::Impl(RunLoop* runLoop_, RunLoop::Type type) : runLoop(runLoop_) {
     using namespace mbgl::android;
     detach = attach_jni_thread(theJVM, &env, platform::getCurrentThreadName());
@@ -105,7 +82,7 @@ RunLoop::Impl::Impl(RunLoop* runLoop_, RunLoop::Type type) : runLoop(runLoop_) {
     case Type::Default:
         ret = ALooper_addFd(loop, fds[PIPE_OUT], ALOOPER_POLL_CALLBACK,
             ALOOPER_EVENT_INPUT, looperCallbackDefault, this);
-        alarm = std::make_unique<Thread<Alarm>>("Alarm", this);
+        alarm = std::make_unique<Alarm>();
         running = true;
         break;
     }
@@ -193,7 +170,7 @@ Milliseconds RunLoop::Impl::processRunnables() {
 
     auto timeout = std::chrono::duration_cast<Milliseconds>(nextDue - now);
     if (alarm) {
-        alarm->actor().invoke(&Alarm::set, timeout);
+        alarm->start(timeout, [this] { wake(); });
     }
 
     return timeout;
diff --git a/platform/android/src/run_loop_impl.hpp b/platform/android/src/run_loop_impl.hpp
index 15cbfa14ae..856a3daba6 100644
--- a/platform/android/src/run_loop_impl.hpp
+++ b/platform/android/src/run_loop_impl.hpp
@@ -15,7 +15,6 @@ struct ALooper;
 namespace mbgl {
 namespace util {
 
-template <typename T> class Thread;
 class Alarm;
 
 class RunLoop::Impl {
@@ -53,7 +52,7 @@ private:
     JNIEnv *env = nullptr;
     bool detach = false;
 
-    std::unique_ptr<Thread<Alarm>> alarm;
+    std::unique_ptr<Alarm> alarm;
 
     std::recursive_mutex mtx;
     std::list<Runnable*> runnables;